Bui. 852, U. S. Dept. of Agriculture. 
Plate XI 
I 
Fig. I. — Interior, Conduit No. 2, Ontario Power Co., Niagara Falls, 
Ontario. 
Note from te::t that form scars were chipped down; then whole surface rubbed down with carborun- 
dum bricks. 
Fig. 2. — Minimum of Erosion by Clear Water. 
After eight years' service the conduit shown in figure 1 has not been eroded sufficiently to obliterate 
paint marks made on walls in 1910. As velocities reach 2S feet per second, this is remarkable 
evidence that good concrete does not erode under sliding contact with clear water. This view taken 
March 31, 1918. 
